336 ME. H. B. GUPPT ON THE THAMES 



winter, to the months of February and March, there are to be 

 always found floating in these rivers, usually in numbers, the 

 carpels of Ranunculus repens and Ranunculus sceleratus ; the nuts 

 of Lycopus europceus and Scutellaria galericulata ; the fruits, en- 

 closed in the perianth, of Atriplex patula, Rumex conglomerates 

 and of two or three other species of Rumex ; the mericarps of 

 Angelica sylvestris\ the nuts of Alnus glutinosa and Betula 

 alba; the drupes of Sparganium ramosum \ the carpels of Alt sma 

 Rlantago ; and the fruits of different species of Carex. Others 

 less frequent, a few of which, however, are certain to be found 

 during this period, when one collects a large amount of material, 

 are the separate black carpels of Galium palustre and the seeds 

 of Iris Rseudacorus. Some fruits, such as the carpels of Sagit- 

 taria sagittifolia and the nuts of Rotamogeton natans, occur 

 frequently in the drift in the autumn but become scanty as the 

 spring comes on. The above remarks apply to both the Thames 

 and the Lea, but it should be added that the Thames is distin- 

 guished from the Lea by the number of the seeds of Impatiens 

 fulva and of the winged seeds of Rhinanthus Crista-galU that float 

 through the winter to the spring ; whilst Bidens achenes are 

 more frequent in the Lea, 



Generally speaking, all the seeds and seed-vessels in the 

 drift of the spring have floated through the winter. This 

 statement is not based merely on their occurrence in the drift 

 of these rivers in the spring but also on a series of parallel ex- 

 periments carried on through the winter indoors. The nuts, 

 however, of the Alder and the Birch form exceptions to this 

 rule. Alder nuts float for many months, but from September 

 to June I have noticed that they are always dropping out of 

 the cones into the water; and in fact most of the nuts found in 

 the drift in the spring have evidently, from their fresh appearance, 

 been only a few weeks in the water. A similar explanation 

 applies to the Birch nuts ; they only float a few days and 

 yet occur in numbers in the drift in the months of February 

 and March. 



"With the exception of the Birch nuts, all the seeds and seed- 

 vessels above named as occurring in the river-drift in the spring 

 germinate in the water in March and April, if not before, and 

 in nearly every case the germination is completed at the surface. 

 It may happen sometimes that germination is delayed till the 

 following year. Thus seeds of Iris Pseudacorus germinated 



